Author Topic: A question for you fridgies  (Read 463 times)

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Offline KeithB

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A question for you fridgies
« on: October 04, 2019, 01:36:49 PM »
I have a 210 litre Evakool 12volt compressor fridge in my caravan. It is well ventilated, but I have installed four 100mm computer fans drawing air through the air outlet at the back. These fans are triggered from a thermostat connected to a thermocouple epoxied onto the copper line coming out of the compressor and into the condenser
I have no idea what the typical temperatures are for this copper line and when to set the fans to turn on and to turn off.
Can anyone advise?
Thanks in advance.
Keith
« Last Edit: October 04, 2019, 02:04:12 PM by KeithB »
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Offline tryagain

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Re: A question for you fridgies
« Reply #1 on: October 04, 2019, 06:38:51 PM »
If the epoxy isn't insulating the temp from the copper, I would probably move it, it's more the ambient temperature in the space that will fluctuate and what I would be concerned about as opposed to the temperature of the fridge components. I would think that 40-50deg would be the kind of ambient temperature I'd want the auxiliary fans to kick in at.
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Offline KeithB

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Re: A question for you fridgies
« Reply #2 on: October 05, 2019, 09:01:31 AM »
That makes sense. If the fridge is working as it should, it shouldn't matter what the temperature is coming out of the compressor, provided that the fridge ventilation is doing its job. But Karls Koolfridge instructions say to put the thermocouple on the copper line ex the compressor, which I dutifully did. I have sent them an email off for clarification.

Since my original post I spoke to the local Evakool repair agent who said that auxiliary fans are a great idea. But he saw no sense in putting the thermocouple where it is. Like you, he says to put it in the air space above the condenser.

I think I'll order a new thermocouple and put it where it should go. No chance of getting the old one off the copper intact.
Keith
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Offline HKB Electronics

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Re: A question for you fridgies
« Reply #3 on: October 05, 2019, 10:45:59 AM »
A fridge works by heat transfer, the liquid refrigerant evaporates in the evaporator and cools it, the cold refrigerant absorbs the heat inside the fridge and changes to a gas state, it then travels to the compressor. The compressor compresses the gas in doing so raises its temperature and pressure, gas then travels to the condenser coils where it is cooled and turns back into a liquid under pressure. The heat from the fridge is transferred to the condenser where it is removed by the cool air flowing around the condenser.

If you can't remove the heat from the condenser coils no cooling will take place, the more heat you remove from the condenser the more efficient the process will be.

When a fridge is designed compromises are made due to costs, space and energy consumption and noise etc. The compressor outlet will be hot but how hot depends on how much heat is absorbed in the fridge and how much heat is removed in the evaporator, if the evaporator removes no heat then no cooling will take place.

You therefore have a balancing act, little cooling at the condenser will result in long compressor run times, lots of cooling at the condenser will give shorter compressor run times, therefore removing the most heat you can from the condenser without unduly increasing the energy consumption will result in more efficient operation. A fridge in a kitchen for instance with a large condenser in a cool environment might be able to remove most of the heat without any fans etc. If you build it into a cupboard then you will probably reduce the air flow and reduce its efficiency. Same if the environmental temperature is high. Adding cooling fans may improve this but you need to ensure the energy consumption of the fans is offset by the reduced cycle times of the compressor or you have achieved nothing.

I have found with small compressor portable fridge freezers (12V) that replacing the cooling fan with two high volume high efficiency units with one pulling and one pushing considerably reduces the run time of the compressor and reduces energy consumption, the down side is increased noise.

With my camper I found due to cabinet design the was a trapped pocket of hot dead air around the condenser, I placed a row of 5 minature industrial vans in the vent in the cabinet that run when the compressor does, these create a slight breeze, you don't really feel it but there is enough pressure created to lift a sheet of paper whereas without the fans there is no lift. These fans have considerably reduce the run time of the compressor and the fridge uses less power with the fans than without.

It really depends on what your trying to achieve, if your just want to increase the fridges cooling performance in hot conditions then a thermostatically controlled fan/s might be the go. If you want to decrease overall energy  consumption ie running off batteries then you may well be better off running the fans whenever the compressor is running rather then having them thermostatically controlled. Down side is there will be increased noise levels.
« Last Edit: October 05, 2019, 10:57:26 AM by HKB Electronics »
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Offline Craig Tomkinson

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Re: A question for you fridgies
« Reply #4 on: October 06, 2019, 07:10:46 AM »
My dads mate fitted a 10cm computer fan to dads old freeser which is mine now a 100lt trailblazer the motor starts then the fan kicks in it runs all the time, it comes off power block, it blows air down over the compressor and pipes I recon in hot weather it makes the freeser 10% better, both freezer  fanrunning  are very quiet, it makes buggerall noise compared to a normal Engel fridge running, 
« Last Edit: October 06, 2019, 07:15:21 AM by Craig Tomkinson »
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Offline geopaj

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Re: A question for you fridgies
« Reply #5 on: October 06, 2019, 07:26:43 AM »
My dads mate fitted a 10cm computer fan to dads old freeser which is mine now a 100lt trailblazer the motor starts then the fan kicks in it runs all the time, it comes off power block, it blows air down over the compressor and pipes I recon in hot weather it makes the freeser 10% better, both freezer  fanrunning  are very quiet, it makes buggerall noise compared to a normal Engel fridge running, 

My fibreglass Evakool is factory set up this way (with a fan) too. A few years ago I added some foam filling around the fan so that all the air moved by the fan is pulled across the compressor and condenser, then expelled (I’d noticed that some air was recirculating and not being expelled.
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Offline chester ver2.0

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Re: A question for you fridgies
« Reply #6 on: October 08, 2019, 08:19:30 AM »
I had the fans on thermostat in the goldstream but could never get the cut in and out quite right so i buggered the thermostat off and just put a manual switch in. When we arrived at camp after having the fridge on 12 volt i would just turn the fans on for an hour or so to get the temp back down.

On really hot days i may just turn then on again when the arvo sun was on the fridge vents

1 of the biggest differences we noticed was when we put a run of sail trak and shade cloth down the off side of the van then as the fridge vents were in shade all day really made a difference
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